Implantable medical devices (IMDs) provide electrical stimulation and/or drug therapy to patients to address medical issues. The IMD is implanted within the body of the patient at a convenient location such as within the abdomen or within the upper torso. An implantable medical lead is coupled to the IMD and may be routed from the site of the implantable medical device to a target site where the electrical stimulation is provided to the tissue, such as within the spinal column, within the brain, and so forth. The IMD generates electrical stimulation signals that are carried by an electrical conductor within the lead to electrodes located at a distal region of the lead that are positioned at the target site.
In order to implant the IMD, a surgical procedure is used where a sterile field is provided about the body. Prior to passing the IMD into the sterile field, an external device may open a far field communication session with the IMD in order to perform preliminary tasks including transferring patient information to the IMD. For instance, the external device may open a MICS band communication session for this purpose. Often during this time, the patient is being prepped for the surgical procedure within the sterile field. Once the preliminary tasks are completed by the external device, the external device may then terminate the communication session. Closing the communication session preserves the battery life of the IMD by allowing the far field communication circuit to sleep. The IMD is then passed into the sterile field and is surgically implanted within the body of the patient.
Once the IMD has been implanted, the external device is then used to open another far field communication session with the IMD. The external device may communicate with the IMD to initiate integrity checks of the leads that are connected to the IMD. The external device may also communicate with the IMD to program the stimulation therapy parameters. The communication session may then be closed and the surgical procedure is concluded.
Because the external device utilizes far field communications with the IMD, it is desirable to ensure that the external device is communicating with the intended IMD. Other IMDs may also be in range of the far field signals of the external device, and the external device should avoid opening far field communication sessions with these other IMDs. To ensure that the external device is communicating with the correct IMD, the external device may use a proximity communication such as a near field inductive communication via a near field wand that only the intended IMD is able to receive. The proximity communication may transfer a unique key from the external device to the IMD. The external device may then ensure that the key is being used by the IMD that is responding via the far field communications such as for encryption purposes or to otherwise identify the communications from the IMD.
This transfer of the key via the proximity communication ensures that the external device is communicating with the correct IMD. However, because the external device of this scenario is not permanently bonded to the IMD, the external device attempts to exchange a new key each time a far field communication session is attempted. Therefore, when the external device attempts to start a far field communication session with the IMD while the IMD is located within the sterile field, the proximity communication requires that the proximity wand be introduced into the sterile field. This introduces additional burdens and delay into the implantation process.